Combined seat and back unit



FIG. 1 is a front elevational view of a combined seat and back unit incorporating our new design;

FIG. 2 is a side elevational view;

FIG. 3 is a top view;

FIG. 4 is a rear elevational view; and

FIG. 5 is a bottom view. 

The ornamental design for a combined seat and back unit, as shown and described. 